Coaxial cables comprise an inner conductor, an outer conductor concentrically disposed around the inner conductor and a non-conducting insulation uniformly disposed therebetween. The cables may or may not include an outer insulation. Coaxial cables are used in many applications where it is necessary to carry radio frequency or microwave frequency electric signals.
Coaxial cables must maintain their symmetry while in use. Variations in coaxial symmetry can create an impedence or a phase shift which can have a substantial degrading effect on the electric signal carried by the cable. To maintain symmetry at an electrical connection, the ends of the coaxial cable typically are joined to coaxial cable connectors which are designed to have a minimum effect on the signal. Coaxial cable connectors may be used to join one cable to another or to join a coaxial cable to an electrical device.
One particular type of coaxial cable includes a center conductor, a symmetrical insulation, such as Teflon, surrounding the center conductor, and a semi-rigid tubular outer conductor, with no insulation extending around the tubular outer conductor. These semi-rigid tubular outer conductor coaxial cables can be joined to coaxial cable connectors by soldering. Although soldered connections are widely used, they present several significant problems. Specifically to make the soldered connection, both the tubular outer conductor and the connector must be heated sufficiently to cause the solder to melt and wick into the area between the two members. This heat causes the insulation to expand, and the expansion can, in turn, cause a permanent deformation of the tubular outer conductor, with a resultant detrimental effect on the signal-carrying performance of the coaxial cable. In extreme instances the heat generated to melt the solder can damage nearby electrical components.
Solderless connectors for tubular outer conductor coaxial cables avoid problems attributable to soldering heat. However, solderless connectors have required a mechanical deformation of the outer conductor. For example, the cable may be inserted into a bushing or sleeve which then is placed in a special tool which crimps both the sleeve and the cable sufficiently to mechanically interengage the two. The crimped sleeve then can be force fit into another part of the connector. This deformation of the outer conductor has a substantial effect on the signal carried by the cable. If the connector is to be used in an environment with severe temperature, shock and vibration conditions, the size of the crimp must be further increased with an even greater degrading effect on electrical performance.
Other solderless coaxial connectors have been developed which rely on compression rather than crimping. However, the net effect is the same in that the geometry changes with a resultant effect on electrical performance. Both the crimping and compression solderless connectors require special tools to mechanically deform the outer conductor of the cable. These tools typically are quite expensive, and if not used properly can twist and permanently damage the cable. Additionally, crimping, compression and soldering all are permanent connections. Thus it is difficult or impossible to disconnect, shorten and reconnect the cable in order to achieve a desired precise phase length.
In view of the above it is an object of the subject invention to provide a connector for tubular outer conductor coaxial cables which does not require soldering or other application of heat to the cable or the connector.
It is another object of the subject invention to provide a solderless connector for tubular outer conductor coaxial cables which does not require special tools and can be connected by hand or with a standard wrench.
It is an additional object of the subject invention to provide a solderless connector for tubular outer conductor coaxial cables which does significantly affect the electrical performance at radio frequency or microwave frequency.
It is a further object of the subject invention to provide a solderless connector for tubular outer conductor coaxial cables which does not crimp or otherwise substantially deform the cable.
It is yet another object of the subject invention to provide a solderless connector for tubular outer conductor coaxial cables which can be easily disconnected and reconnected.
It is yet an additional object of the subject invention to provide a solderless connector for tubular outer conductor coaxial cables which can be employed under severe conditions of temperature, shock, and vibration.